1. Field of the Invention
This invention relates to an apparatus for controlling the flow of air for external cooling of a tubular film, issuing from an extruder head.
2. Description of the Prior Art
Such an apparatus is known from U.S. Pat. No. 4,209,475. In the known apparatus the air for external cooling is supplied through the extruder head in passages, which are disposed radially outwardly of the die through which the extrudate is discharged from the extruder head, and longitudinally adjustable, upwardly inclined plates extend into said passages.
The known apparatus can be used only when the extruder is operated in the so-called "short-neck" mode. On the other hand, if a tubular film is to be extruded in the so-called "long-neck" mode, the known apparatus will no longer be sufficient because in that case the region in which the tubular film is expanding is too far away from the extruder head so that the known apparatus can no longer act on said region.